March 14 is Pi Day. It is observed on March 14 since 3, 1, and 4 are the first three significant digits of the math symbol π. Don’t let the sound of the name fool you: Pi Day does not commemorate the sweet, baked circular treat (though it is circular-related). It is the official day of the Greek letter symbolizing the ratio of the circumference of a circle to its diameter, pi, also known as 3.14159265359… Pi Day is an annual celebration of the mathematical constant π. Below are some fun ways to incorporate learning and to celebrate Pi Day.